1. Field of the Invention
The present invention relates to a wireless communication apparatus capable of performing power supply control of a terminal.
2. Description of Related Art
With development of LAN (Local Area Network) technology, networking of information equipment, household electrical appliances and the like has been advancing. Recently, it is common to build a network by combining a wired LAN and a wireless LAN.
For example, a wireless base station is connected to a wired LAN, and the base station is connected to multiple terminals via a wireless LAN. Such a wireless LAN is advantageous in that wiring laying is not required because radio waves, infrared rays or the like is used as a transmission line, and, therefore, it is easy to newly build a network or change layout.
Introduction of such a wireless LAN has been spurred by standardization by IEEE802.11. In IEEE802.11, specifications for 2.4 GHz band wireless LAN and specifications for 5 GHz band wireless LAN were completed in 1997 and 1999, respectively. In these wireless LAN specifications, lower power consumption technology is also standardized.
There is a possibility that a wireless communication apparatus in conformity with the IEEE802.11 standards is used in various environments. For example, it is conceivable that the wireless communication apparatus is used to build a home network in a home. In a home network, a station (hereinafter, also referred to as a STA), such as a digital TV, a DVD and a PC, wirelessly accesses an access point (hereinafter, also referred to as an AP) of a home server or the like. Thereby, wireless communication of data, such as an AV stream and a PC network stream, becomes possible between the STA and the AP.
In the IEEE802.11 standards, an access point manages each station within a wireless network. For this management, the access point assigns an association number to each station and transmits a management frame (beacon frame) to each station.
On the other hand, each station may operate in a power save mode in which a power supply for a wireless function is turned off to lower power consumption. Even in this case also, each station needs to receive the beacon frame in a predetermined cycle according to the beacon cycle in order to check whether there is data destined to the station itself, which has been relayed via the access point. That is, each station needs to turn on the power supply for the wireless function at least in the predetermined cycle to receive the beacon frame.
However, in actual use of a home network apparatus constituting a station, it is necessary to turn on the power supply for the wireless function when a power supply for main body functions is turned on or only for a extremely limited period, and the specification specifying that the power supply is turned on each predetermined cycle cannot achieve sufficient low power consumption.
Accordingly, it is conceivable to enable each station to perform an intermittent operation by accepting a wireless wakeup signal from the access point only when necessary. In order to enable such an intermittent operation, power is continuously supplied only to a part which controls the power supply for the wireless function, between the main body functions and the wireless function of each station, and the power supply for the wireless function is turned on by a wakeup signal. Thereby, it is possible to achieve sufficiently low power consumption. For example, Japanese Patent Application Laid-Open Publication No. 08-116289 discloses an apparatus which wakes up in response to obtaining a detection output with a predetermined strength.
It is also necessary to realize sufficiently low power consumption for the part which controls the power supply for the wireless function because it is necessary to continuously supply power to the part. However, it is conceivable that, if it is attempted to reduce power consumption of the part which controls the power supply for the wireless function, sensitivity of receiving a wakeup signal decreases for the reason of circuit configuration, a wakeup signal detection error occurs, and the power supply for the wireless function cannot be turned on.